The generic term "scroll machine" encompasses a class of positive fluid displacement apparatus which use orbiting involute spiral wraps formed on facing parallel plates to compress, expand, or pump a fluid. Although many designs for scroll machines exist in the prior art, very few have been successfully reduced to practice as commercially viable products. Some of the problems which have arisen in these development attempts are unique to the scroll machine, e.g., providing effective seals between the involute wraps and the end plates. However, other more common problems involving the efficiency and operating life of scroll machines must also be solved. For example, as in any mechanical device having moving parts subject to friction and wear, it is necessary to provide proper lubrication. In a scroll machine, an adequate lubricant supply is particularly important for the bearings associated with the rotating drive shaft and with the elements for converting the rotational motion of the shaft into the orbital motion of the scroll plates.
The lubrication system used in scroll machines and other rotating machinery having vertical drive shafts generally follow a similar pattern. Typically in such machines, oil flows from a reservoir located in either the lower or upper part of the machine housing, through oil passages drilled in the drive shaft, for distribution to the various components requiring lubrication. An example of such a scroll machine is disclosed in U.S. Pat. No. 4,065,279, wherein a centrifugal oil pump forces oil up through two eccentrically placed oil passages in a vertical drive shaft. One of these passages supplies oil to a series of grooves associated with a swing link journal bearing, thereby lubricating it and an adjacent thrust bearing. Oil flowing in the second internal passage of the drive shaft is distributed through a right angle passage for lubrication of the top journal bearing of the drive shaft. This design illustrates a problem common to scroll machines--providing adequate lubrication to the thrust, swing link, and drive shaft bearings--difficult due to the spacial separation of these bearings and their relatively dissimilar motion.
Laboratory tests of the lubrication system disclosed in the U.S. Pat. No. 4,065,279 patent have shown that the upper drive shaft journal bearing does not receive sufficient lubrication. This is believed due partly to an inadequate volumetric flow output from the centrifugal oil pump and partly to improper allocation of the oil flow between the drive shaft bearing and the other bearings. Allocation of oil between the thrust and swing link bearings is not a problem in the design of the U.S. Pat. No. 4,065,279 patent since oil for lubricating the thrust bearing first flows through the groove in the swing link bearing. However, where separate oil passages are used to supply oil to these bearings, the oil flow must be properly allocated between them.
A further problem noted in the lubrication of scroll machines concerns the lack of initial lubrication when such machines are restarted after a period of disuse. Typically, when a scroll machine stops operating, almost all of the lubricating oil drains down from the bearings and back into the reservoir. When the machine is restarted, oil is not available to lubricate bearing surfaces until it is distributed throughout the oil passages of the lubrication system. The longer and more tortuous the route which the oil must follow to reach these surfaces, the more likely it is that undesirable wear will occur, thereby shortening the operational life of the scroll machine.
In view of the foregoing discussion, it is therefore an object of this invention to provide an oil distribution and lubrication system for a scroll machine which minimizes wear of its bearings and prolongs its useful life.
It is a further object of this invention to properly distribute and allocate oil between the various bearings of a scroll machine.
A still further object of this invention is to make oil immediately available to lubricate bearings of the scroll machine when it is restarted after having been de-energized for a period of time.
These and other objects of the invention will become apparent from the description of the preferred embodiment which follows, and by reference to the attached drawings.